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[InstCombine] improve folds for icmp with multiply operands (PR47432)

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Check for no overflow along with an odd constant before
we lose information by converting to bitwise logic.

https://rise4fun.com/Alive/2Xl

  Pre: C1 != 0
  %mx = mul nsw i8 %x, C1
  %my = mul nsw i8 %y, C1
  %r = icmp eq i8 %mx, %my
  =>
  %r = icmp eq i8 %x, %y

  Name: nuw ne
  Pre: C1 != 0
  %mx = mul nuw i8 %x, C1
  %my = mul nuw i8 %y, C1
  %r = icmp ne i8 %mx, %my
  =>
  %r = icmp ne i8 %x, %y

  Name: odd ne
  Pre: C1 % 2 != 0
  %mx = mul i8 %x, C1
  %my = mul i8 %y, C1
  %r = icmp ne i8 %mx, %my
  =>
  %r = icmp ne i8 %x, %y
This commit is contained in:
Sanjay Patel 2020-09-07 12:37:59 -04:00
parent 1fd12b30bd
commit c688e87b99
2 changed files with 32 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -3983,6 +3983,19 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
ConstantExpr::getNeg(RHSC));
}
{
// Try to remove shared constant multiplier from equality comparison:
// X * C == Y * C (with no overflowing/aliasing) --> X == Y
Value *X, *Y;
const APInt *C;
if (match(Op0, m_Mul(m_Value(X), m_APInt(C))) && *C != 0 &&
match(Op1, m_Mul(m_Value(Y), m_SpecificInt(*C))) && I.isEquality())
if (!C->countTrailingZeros() ||
(BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap()) ||
(BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap()))
return new ICmpInst(Pred, X, Y);
}
BinaryOperator *SRem = nullptr;
// icmp (srem X, Y), Y
if (BO0 && BO0->getOpcode() == Instruction::SRem && Op1 == BO0->getOperand(1))
@ -4059,10 +4072,6 @@ Instruction *InstCombinerImpl::foldICmpBinOp(ICmpInst &I,
Value *And2 = Builder.CreateAnd(BO1->getOperand(0), Mask);
return new ICmpInst(Pred, And1, And2);
}
// If there are no trailing zeros in the multiplier, just eliminate
// the multiplies (no masking is needed):
// icmp eq/ne (X * C), (Y * C) --> icmp eq/ne X, Y
return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
}
break;
}

46
test/Transforms/InstCombine/icmp-mul.ll
View File

@ -392,8 +392,7 @@ define i1 @mul_constant_ne_extra_use1(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_constant_ne_extra_use1(
; CHECK-NEXT: [[A:%.*]] = mul i8 [[X:%.*]], 5
; CHECK-NEXT: call void @use(i8 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul i8 [[Y:%.*]], 5
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[X]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul i8 %x, 5
@ -405,10 +404,9 @@ define i1 @mul_constant_ne_extra_use1(i8 %x, i8 %y) {
define i1 @mul_constant_eq_extra_use2(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_constant_eq_extra_use2(
; CHECK-NEXT: [[A:%.*]] = mul i8 [[X:%.*]], 5
; CHECK-NEXT: [[B:%.*]] = mul i8 [[Y:%.*]], 5
; CHECK-NEXT: call void @use(i8 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[X:%.*]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul i8 %x, 5
@ -424,7 +422,7 @@ define i1 @mul_constant_ne_extra_use3(i8 %x, i8 %y) {
; CHECK-NEXT: call void @use(i8 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul i8 [[Y:%.*]], 5
; CHECK-NEXT: call void @use(i8 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul i8 %x, 5
@ -437,9 +435,7 @@ define i1 @mul_constant_ne_extra_use3(i8 %x, i8 %y) {
define i1 @mul_constant_eq_nsw(i32 %x, i32 %y) {
; CHECK-LABEL: @mul_constant_eq_nsw(
; CHECK-NEXT: [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[TMP1]], 2147483647
; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[TMP2]], 0
; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nsw i32 %x, 6
@ -450,9 +446,7 @@ define i1 @mul_constant_eq_nsw(i32 %x, i32 %y) {
define <2 x i1> @mul_constant_ne_nsw_splat(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @mul_constant_ne_nsw_splat(
; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = and <2 x i32> [[TMP1]], <i32 1073741823, i32 1073741823>
; CHECK-NEXT: [[C:%.*]] = icmp ne <2 x i32> [[TMP2]], zeroinitializer
; CHECK-NEXT: [[C:%.*]] = icmp ne <2 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret <2 x i1> [[C]]
;
%A = mul nsw <2 x i32> %x, <i32 12, i32 12>
@ -465,8 +459,7 @@ define i1 @mul_constant_ne_nsw_extra_use1(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_constant_ne_nsw_extra_use1(
; CHECK-NEXT: [[A:%.*]] = mul nsw i8 [[X:%.*]], 74
; CHECK-NEXT: call void @use(i8 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul nsw i8 [[Y:%.*]], 74
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[X]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nsw i8 %x, 74
@ -478,10 +471,9 @@ define i1 @mul_constant_ne_nsw_extra_use1(i8 %x, i8 %y) {
define i1 @mul_constant_eq_nsw_extra_use2(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_constant_eq_nsw_extra_use2(
; CHECK-NEXT: [[A:%.*]] = mul nsw i8 [[X:%.*]], 20
; CHECK-NEXT: [[B:%.*]] = mul nsw i8 [[Y:%.*]], 20
; CHECK-NEXT: call void @use(i8 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[X:%.*]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nsw i8 %x, 20
@ -497,7 +489,7 @@ define i1 @mul_constant_ne_nsw_extra_use3(i8 %x, i8 %y) {
; CHECK-NEXT: call void @use(i8 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul nsw i8 [[Y:%.*]], 24
; CHECK-NEXT: call void @use(i8 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nsw i8 %x, 24
@ -510,9 +502,7 @@ define i1 @mul_constant_ne_nsw_extra_use3(i8 %x, i8 %y) {
define i1 @mul_constant_nuw_eq(i32 %x, i32 %y) {
; CHECK-LABEL: @mul_constant_nuw_eq(
; CHECK-NEXT: [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[TMP1]], 2147483647
; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[TMP2]], 0
; CHECK-NEXT: [[C:%.*]] = icmp eq i32 [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nuw i32 %x, 22
@ -523,9 +513,7 @@ define i1 @mul_constant_nuw_eq(i32 %x, i32 %y) {
define <2 x i1> @mul_constant_ne_nuw_splat(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @mul_constant_ne_nuw_splat(
; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = and <2 x i32> [[TMP1]], <i32 2147483647, i32 2147483647>
; CHECK-NEXT: [[C:%.*]] = icmp ne <2 x i32> [[TMP2]], zeroinitializer
; CHECK-NEXT: [[C:%.*]] = icmp ne <2 x i32> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: ret <2 x i1> [[C]]
;
%A = mul nuw <2 x i32> %x, <i32 10, i32 10>
@ -538,8 +526,7 @@ define i1 @mul_constant_ne_nuw_extra_use1(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_constant_ne_nuw_extra_use1(
; CHECK-NEXT: [[A:%.*]] = mul nuw i8 [[X:%.*]], 6
; CHECK-NEXT: call void @use(i8 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul nuw i8 [[Y:%.*]], 6
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[X]], [[Y:%.*]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nuw i8 %x, 6
@ -551,10 +538,9 @@ define i1 @mul_constant_ne_nuw_extra_use1(i8 %x, i8 %y) {
define i1 @mul_constant_eq_nuw_extra_use2(i8 %x, i8 %y) {
; CHECK-LABEL: @mul_constant_eq_nuw_extra_use2(
; CHECK-NEXT: [[A:%.*]] = mul nuw i8 [[X:%.*]], 36
; CHECK-NEXT: [[B:%.*]] = mul nuw i8 [[Y:%.*]], 36
; CHECK-NEXT: call void @use(i8 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[X:%.*]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nuw i8 %x, 36
@ -570,7 +556,7 @@ define i1 @mul_constant_ne_nuw_extra_use3(i8 %x, i8 %y) {
; CHECK-NEXT: call void @use(i8 [[A]])
; CHECK-NEXT: [[B:%.*]] = mul nuw i8 [[Y:%.*]], 38
; CHECK-NEXT: call void @use(i8 [[B]])
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[A]], [[B]]
; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[X]], [[Y]]
; CHECK-NEXT: ret i1 [[C]]
;
%A = mul nuw i8 %x, 38
@ -581,6 +567,8 @@ define i1 @mul_constant_ne_nuw_extra_use3(i8 %x, i8 %y) {
ret i1 %C
}
; Negative test - wrong pred
define i1 @mul_constant_ult(i32 %x, i32 %y) {
; CHECK-LABEL: @mul_constant_ult(
; CHECK-NEXT: [[A:%.*]] = mul i32 [[X:%.*]], 47
@ -594,6 +582,8 @@ define i1 @mul_constant_ult(i32 %x, i32 %y) {
ret i1 %C
}
; Negative test - wrong pred
define i1 @mul_constant_nuw_sgt(i32 %x, i32 %y) {
; CHECK-LABEL: @mul_constant_nuw_sgt(
; CHECK-NEXT: [[A:%.*]] = mul nuw i32 [[X:%.*]], 46
@ -607,6 +597,8 @@ define i1 @mul_constant_nuw_sgt(i32 %x, i32 %y) {
ret i1 %C
}
; Negative test - wrong constants
define i1 @mul_mismatch_constant_nuw_eq(i32 %x, i32 %y) {
; CHECK-LABEL: @mul_mismatch_constant_nuw_eq(
; CHECK-NEXT: [[A:%.*]] = mul nuw i32 [[X:%.*]], 46